Which one of the following is NOT an example of bio-mass energy source ?

Question

UnlockIAS · Accepted Answer

Correct — A, Nuclear energy. Biomass means organic matter of biological origin burnt or digested for its stored chemical energy — energy that traces back to photosynthesis. Nuclear energy has nothing to do with any of that: it is released when heavy nuclei such as uranium-235 or plutonium-239 are split in a reactor, converting a tiny fraction of nuclear binding mass into heat. No plant, no animal and no photosynthesis is involved anywhere in the chain, so nuclear energy is the one option that stands entirely outside the biomass family. Wood (b) and gobar (d) are the textbook examples of biomass and are clearly wrong choices here. Be aware, though, that this item has a second defensible answer: under the standard classification used in science and energy-policy texts, coal (c) is a fossil fuel, not biomass — the two categories are listed separately, alongside petroleum and natural gas. The commission's key marks (a), and (a) is the stronger answer because coal at least began as plant material while nuclear fuel never did; but a candidate who chose (c) had a real case. Marks follow the official key, so (a) it is.

Why the other options are wrong — (b) Wood is the oldest and most widely used biomass fuel on earth. Its energy is carbon fixed by a tree through photosynthesis over years or decades, and burning it releases that energy back. It is squarely inside the category the question asks you to step outside of.  (c) Not the keyed answer, but the honest position is that this is the paper's weak point rather than the candidate's. Coal did begin as plant matter — peat-forming swamp vegetation compressed and heated over tens to hundreds of millions of years — which is presumably why the commission treats it as belonging with the biomass family. Standard classifications, however, place coal with petroleum and natural gas as a fossil fuel and keep biomass separate, precisely because coal's carbon left the living cycle in the geological past and is not renewable on any human timescale. So (c) is defensible on the science; (a) is what the key marks, and (a) remains the cleaner answer because nuclear energy has no organic origin at all.  (d) Cattle dung is biomass twice over — it is animal waste made of partly digested plant matter. Dried into cakes it is burnt directly in rural households, and fed into a digester it yields biogas. Either way the energy came from grass and fodder, that is, from photosynthesis.

Concept: Energy sources are sorted first by whether they renew on a human timescale and then by origin. Biomass is renewable organic matter of recent biological origin: firewood, crop residue, bagasse, dung, and the biogas or ethanol made from them. Fossil fuels — coal, petroleum, natural gas — are also of organic origin, but the organisms died hundreds of millions of years ago and the deposits are not replaced as we burn them, which is why they sit in a category of their own. Nuclear energy belongs to neither: it comes from the nucleus of heavy atoms, not from chemical bonds built by living things, and its fuel is a mined mineral.

State PCS 2022 Q24 — Science & Technology PYQ with Answer

State PCS 2022 Q24 — Science & Technology PYQ with Answer